1. Field of the Invention
The instant disclosure relates to a sealing element and wound-type solid state electrolytic capacitor thereof; in particular, to a sealing element and wound-type solid state electrolytic capacitor therefor for acoustics
2. Description of Related Art
For acoustics components, capacitors are widely used for filtering, decoupling, high-frequency compensation, and providing direct feedback. Depending on the structure and manufacturing process, capacitors can be divided into a variety of classes. Specifically in audio systems, since characteristics such as large frequency response and current are required, thus, aluminum electrolytic capacitors are most widely used.
As shown in FIG. 12, the conventional wound-type solid state electrolyte capacitor comprises a capacitor casing 1, a capacitor element 2, and the sealing member 3. One end of the capacitor casing has an open end, the sealing element 3 is disposed in the open end and forms a hermetic seal with the open end, so that the capacitor element 2 remains inside the capacitor casing 1. Capacitor element 2 is connected to two terminals 4 and is soldered to the circuit board via the two terminals 4.
The capacitor element 2 is an anode foil wound together with a cathode foil, and an electrolyte layer is formed between the anode foil and the cathode foil. The anode foil and the cathode foil of the capacitor element are dielectric layers made from oxidized metal thin films, or by depositing insulating polymer materials, via vapor deposition, onto the conductive layer. The anode foil and the cathode foil have a dielectric thin film or an insulating thin film therebetween, so that insulation is formed between the anode foil and the cathode foil of the capacitor.
Typical capacitors are reflow-soldered onto the circuit board. During soldering, the capacitor must pass through a high heat soldering furnace, thus, the capacitor must also endure high temperatures. Since the capacitor casing 1 is a closed-off environment and the encapsulated capacitor element 2 is impregnated with electrolytes and polymer material for establishing insulation, heated electrolytes or polymer material may become volatile gases that can build up pressure inside the capacitor casing 1, and the capacitor element 2 and the sealing element 3 inside the capacitor casing 1 might undergo stress and deformation due to the buildup of internal pressure.
When the capacitor element 2 undergoes thermal deformation, if the element is compressed onto the inside surface of the sealing element 3, the capacitor element will undergo stress due to deformation that may damage the insulation layer or dielectric layer of the capacitor element 2, and may result in current leakage. On the other hand, the hermetic seal between sealing element 3 and capacitor casing 1 maybe be destroyed due to compression by the capacitor element 2, such that moisture or other impurities may enter the capacitor casing, which can damage the insulation of the capacitor element 2.
Conventionally, in order to prevent the thermal deforming capacitor element 2 from compressing the surface of the sealing element 3, a gap is typically maintained between the capacitor element 2 and the sealing element. However, the gap tends to allow the capacitor element 2 to sway within the capacitor casing 1, which can lead to changes in electrical characteristics of the capacitor element, such as stability of current and impedance.
Furthermore, when the capacitor is soldered to the circuit board, the two terminals of the capacitor 4 are installed on the circuit board in the direction of one end of the sealing element 3, whereas the terminals 4 of the capacitor and the circuit board are connected by soldering. In the conventional capacitor structure, since the end surface of the sealing element 3 is planar, when the end is installed onto the circuit board, the end surface of the sealing element 3 may have direct contact with the outer surface of the circuit board. As such, problems might surface such as (1) during soldering the capacitor, internal pressure of the capacitor case might increase as the temperature rises within, the sealing member 3 might be pressed outwards, so that the end surface of the sealing element 3 is pressed against the circuit board, which can result in deformation to the circuit board or damages to capacitor terminals; (2) the end surface of the sealing element 3 makes contact with the outer surface of the circuit board, which eliminates any room for gases generated to flow when the capacitor terminals 4 are soldered to the circuit board. At the same time, soldering may generate capillary action due to the gap between the end surface of the sealing element and the circuit board 3 to be too small that can cause unintended solder flow and in turn result in soldering defects at the capacitor terminals 4.
For these reasons, the conventional wound-type solid state electrolyte capacitor has a considerable amount of operational defects. With improvements in structural design, the method to overcome these defects, which can reduce the adverse effects of a wound-type solid state electrolyte capacitor due to the high soldering temperature during soldering, has become an important subject to be resolved.
To address the above issues, the inventor strives via associated experience and research to present the instant disclosure, which can effectively improve the limitation described above.